262 EXISTING INDIAN ELEPHANT. 



instead of being perpendicular to the axis of the wedges, cuts 

 them obliquely, the obliquity increasing with the advance of 

 wear and constantly tending towards the horizontal. The 

 consequence is, that the width of the discs is always ex- 

 aggerated hi a tooth worn down to the base, and that the 

 anterior discs are wider than the hinder ones. The only 

 accurate method of ascertaining the number of ridges within 

 a given space is to measure the crown, not at the summit, 

 but along the base where the enamel-plates are reflected ; the 

 product will then give the average width of each ridge. The 

 skull of the Ceylon Elephant (No. 2656, Coll. Surg.), supplies 

 excellent and readily accessible materials for testing the 

 value of the alleged character, in the so-called E. Sumatranus. 

 It contains, above and below, the penultimate and last true 

 molars in action ; the former in advanced wear, the latter 

 coming into use, and in the upper jaw barely abraded. The 

 right upper penultimate is worn low, with a loss of the 

 anterior portion. The crown presents the discs of eight 

 distinct ridges, together with a denuded base of ivory in 

 front, corresponding with two ridges that have been worn 

 out. These discs are wide, with highly crimped enamel 

 machcerides, both being of the E. Sumatranus pattern. The 

 following are the principal dimensions : — 



Length of crown measured at summit, 8* in. Space occupied by the 7 last discs 

 of wear, 58 in. Greatest width of crown, 3'0 in. 



In this case the discs are very open, with an average width 

 of about '83 inches to each ; but in the progress of wear, the 

 ridge-plates have become so reclinate, in relation to the 

 plane of detrition, that in the middle of the crown, from the 

 causes above assigned, the grooved enamel-plates are ex- 

 posed nearly horizontally, to the extent of nine-tenths of an 

 inch. The width of the bands, in this instance, is an ex- 

 aggeration arising from the obliquity of the section yielding 

 them, in a tooth far advanced in wear. 



The last true molar of the same skull makes a different ap- 

 pearance. Although partly extruded it is hardly touched by 

 wear, and the outer wall of the alveolus was removed to 

 expose the concealed hinder portion. The crown is composed 

 of 22 ridge-plates, of which 18 are consolidated, the 4 

 hindmost being loose. It yields the following dimen- 

 sions : — 



Extreme length, measured diagonally, from apex of front ridge to base of the 

 last ditto, 13' in. Length of ditto, measured along the base of the ridges, ll - 5 in. 

 Greatest width, 3 - l in. 



Instead, therefore, of '83 yielded by the penultimate, the 

 ridges in this case give only an average of "52 inches ; and in 

 weighing the result it should be borne in mind that the 



